1. Field of the Invention
The present invention relates to a mass storage device for information processing, video disk recorders for home use and the like and, more particularly, to an optical reproduction device, a recording medium and a method of tracking used for recording and reproducing data on and from, for example, a digital video disk (DVD) as an optical disk recording and reproducing apparatus utilizing an optical beam.
2. Description of the Related Art
The advance of multi-media oriented toward an advanced information society has resulted in a need for optical disks having higher performance and larger capacities. Such optical disks can be generally classified based on the functions and usages thereof into three types, i.e., a read-only optical disk used only for reproducing information data recorded at the time of disk cutting, a write-once type optical disk which allows recording only once and allows no rewriting, and a rewritable optical disk which can be rewritten many times.
Especially, in the case of the rewritable optical disks which allow rewriting of information and data, the need for larger capacities has made it impossible to meet a required recording capacity by using only a groove recording method wherein information data are recorded only in a groove portion comprised of a groove spirally provided on the surface of an optical disk, and therefore a land-groove recording method has been employed wherein information data are recorded also on a region referred to as a land portion provided between the groove portions.
That is, in an optical disk recording and reproducing apparatus, in order to record information data on a predetermined track on an optical disk, an optical pick-up must be moved onto a target track on the optical disk to irradiate the target track with a laser beam. In order to do this, the optical pick-up must be positioned on the target position. Servo systems for moving an optical pick-up to a target position of an optical disk in the radial direction thereof include a tracking servo system.
A tracking servo system comprises a tracking coil and a tracking servo circuit included in an actuator system in an optical pick-up. The actuator system allows an optical pick-up to carry out a tracking operation accurately by means of, for example, a dual spindle actuator.
A track is tracked and the address of the same is read by means of a laser beam that traces the same, and fine seeking is performed in accordance with a difference between the address and a target address to that extent. Since an excessive eccentric speed makes it difficult to control the seek in a stable manner, the target track is finally reached after waiting until the eccentric speed is sufficiently reduced, and a recording operation is performed using land-groove recording wherein information and data are recorded on land portions between groove portions on an optical disk.
FIG. 1 shows a double-spiral groove on an optical disk used for a conventional land-groove recording method.
In FIG. 1, there is formed a groove G that constitutes one spiral guide groove extending from the inner circumference of an optical disk 110 to the outer circumference thereof. There is also formed a land L between the adjacent grooves G.
To record a recording mark on the groove G and land L on such optical disk 110, the recording mark is first recorded sequentially on the groove G from the inner circumference of the optical disk, i.e., on a track 1, a track 3, a track 5, a track 7, and so on with a record or address given and, when the recording is completed out to the outer circumference, the record mark is provided sequentially on the land L from the inner circumference of the optical disk, i.e., on a track 2, a track 4, a track 6, and so on with a record or address, up to the outer circumference where the recording is completed.
FIG. 2 shows a single spiral groove on an optical disk used in the conventional land-groove recording method.
In FIG. 2, there is formed grooves G that constitute a plurality of guide grooves that extend in the form of a spiral from the inner circumference of an optical disk 120 to the outer circumference thereof and terminate at each turn of the optical disk, i.e., at each 360 degrees. Lands L are formed between adjacent grooves G.
To record a recording mark on the grooves G and lands L on such an optical disk 120, the record mark is provided sequentially from the inner circumference of the optical disk toward the outer circumference where the recording is completed, i.e., on a track 1 for the groove G, a track 2 for the land L, a track 3 for the groove G, a track 4 for the land L, a track 5 for the groove G, a track 6 for the land L, a track 7 for the groove G, and so on with a record or address given.
In the case of an optical reproduction apparatus that utilizes the conventional double-spiral groove as shown in FIG. 1, the track 1, track 3, track 5, track 7 and so on are recorded in this order for the groove G up to the outer circumference, and about the land L, the track 2, track 4, track 6 and so on are continuously recorded on sequentially in this order again from the inner circumference. This is difficult to use in cases where continuous recording is required and intermittent recording is prohibited as in the case of the recording of video data. In addition, to record such video data, first video data must continuously be recorded in the grooves G and then the video data must be continuously recorded on the lands L, thereby the video data are continuously recorded on both of the groove G and the land L. This has resulted in a problem in that a buffer having a large capacity is required for temporary storage of data in order to prevent the continuous data from being interrupted during the movement of an optical pick-up from the groove G to the land L.
Further, in the case of an optical reproduction apparatus utilizing the conventional single-spiral groove as shown in FIG. 2, the recording on the track 1 for the groove G is continuously followed by the recording on the track 2 for the land L. The grooves G and the lands L must be molded such that they terminate at each turn of the optical disk, and this has resulted in a problem in that the manufacture of the optical disk 120 itself has a technical difficulty encountered in the process of molding the disk.